I recently moved into a house with an inground hot tub, found out the shell was made by Beachport, Carmel model. I opened it and found bubbles and a very large part of the hot tub surface pulling away at the bottom.

Question: Is this repairable or do I need to get a new shell? My estimate is that the equipment is at least 10 years old. Pictures show my attempt to clean up the stains.

Any suggestions/recommendations are very welcome!

The bubbles in the shell are common for older tubs, and unless they break open and create a sharp edge, or if they crack into a jet gasket surface, they usually aren't much to worry about. You can patch them with epoxy when they do crack or break, but it will never be pretty again. At this point it is strictly up to you wether to invest in a new shell or just enjoy the existing one as it is.